JP7503958B2 - Dental files - Google Patents

Description

The present invention relates to a dental file used to enlarge and clean root canals in dental treatment.

Dental root canal cutting tools used in dental treatment to enlarge and clean root canals include reamers and files. Reamers cut inside the root canal primarily by rotating, while files cut inside the root canal by rotating and pushing and pulling in the axial direction.

Common dental files include those that are held by hand and those that are connected to a dental handpiece. A dental file has a working part that is spiral and tapered toward the tip, a shaft connected to the rear end of the working part, and a grip connected to the rear end of the shaft. The main performance required of such dental files is flexibility to follow the complex shape of root canals, cutting ability to properly cut the root canal, and fracture resistance to prevent breakage during operation. The higher these performances, the easier and faster the root canal formation can be performed, reducing the burden on the practitioner and patient.

As an example of the cross-sectional shape of the dental file described above, one that is formed in the shape of a parallelogram is known (see, for example, Patent Document 1).

Patent No. 6370373

In view of the above circumstances, the present invention aims to improve the flexibility, cutting ability, and/or breakage resistance of dental files.

In order to achieve the above object, the present invention provides
1. A dental file having a spirally shaped working portion,
A cross-sectional shape perpendicular to the longitudinal direction is a trapezoid having an upper base, a lower base, and first and second oblique sides;
With respect to an imaginary circle whose center is the longitudinal axis and whose diameter decreases from the base end to the tip end,
The vertices of both ends of the lower base are located on the virtual circle,
The vertices of both ends of the upper base are set to be located inside the imaginary circle.

As a result, the vertices of the two acute angles that are located on a virtual circle and have a large effect on cutting are not on a diagonal line, and the diagonal vertices of each acute angle are located inside the virtual circle, making it easier to prevent stretching and breakage due to biting lock.

The present invention can improve the flexibility, cutting ability, and/or breakage resistance of dental files.

FIG. 2 is a plan view of the dental file of the first embodiment. 2 is a cross-sectional view taken along line II-II of FIG. 1. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2 is a cross-sectional view taken along line VV in FIG. 1. 1 according to a second embodiment. FIG. 10 is a cross-sectional view of the vicinity of a tip portion of the working unit 100a of FIG. 1 according to a third embodiment. FIG. 1 according to a fourth embodiment. FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that in the following embodiments and variations, components having similar functions will be given the same reference numerals and descriptions thereof will be omitted.

(Embodiment 1)
1, the dental file 100 has a working part 100a for cutting the root canal, a shaft 100b connected to the rear end of the working part 100a, and a gripping part (not shown) connected to the rear end of the shaft 100b and attached to a dental handpiece. The material of the dental file 100 is often, for example, nickel titanium, which has high elasticity and is suitable for treating complexly curved root canals, but is not limited to this, and stainless steel, various alloys, plastics, etc. can also be used.

The working part 100a of the dental file 100 has an outer envelope surface that is tapered in cross section toward the tip, and has a configuration in which similar cross sections are formed in a spiral shape. More specifically, the cross section of the working part 100a perpendicular to the longitudinal direction is formed in a trapezoidal shape as shown in Figures 2 to 5, for example, in the cross sections taken along lines II-II to V-V in Figure 1. That is, the cross section has an upper base 111 and a lower base 112 that are parallel to each other, and a first oblique side 113 and a second oblique side 114 that are connected to the vertices 121 to 124 at both ends of the bases.

The vertices 123 and 124 at both ends of the lower base 112 are located on an imaginary circle 101 whose center is the longitudinal axis of the dental file 100, and the vertices 121 and 122 at both ends of the upper base 111 are set to be located inside the imaginary circle 101. The diameter of the imaginary circle 101 is set to become smaller from the base end to the tip end of the working part 100a. Here, the upper base 111, the lower base 112, and the oblique sides 113 and 114 do not necessarily have to be exact straight lines, and even if they are slightly curved, the effects described below can be obtained. Here, for convenience, in Figures 2 to 5, the imaginary circles 101 are drawn to a scale such that the diameters are equal.

By adopting a trapezoidal cross section as described above, the vertices 123 and 124 of the two acute angles that are located on the imaginary circle 101 and have a large effect on cutting are not on the diameter of the imaginary circle 101 (on a straight line passing through the center O of the imaginary circle 101), making it easier to suppress elongation and breakage due to biting lock.

In addition, since the apexes 123 and 124 make it easy to obtain high cutting performance, the file easily advances through the root canal without being pushed in, making it less likely to deviate from the root canal. In other words, since there is no need to forcefully push the file in, it is easy to prevent the file from deviating to the outside of the root canal curvature. In this way, by forming a file with a trapezoidal cross section, it is easy to achieve both high cutting performance due to the acute angle, as in the case of a parallelogram cross section, while also making it difficult to lock the file because the acute angle is not on the diameter of the imaginary circle 101.

Furthermore, for example, when cutting the cutting groove by pressing a grindstone against it, it is possible to maintain high rigidity and facilitate stable cutting. That is, for example, if the lower base 112 is cut first from the cross-sectional shape of the imaginary circle 101, the outer diameter part of the imaginary circle 101 on the opposite side (upper base side) can receive the pressing force of the grindstone, and when cutting the upper base 111 or the oblique sides 113 and 114, the vertices 123 and 124 on the opposite side can easily receive the pressing force of the grindstone. This makes it easy to perform cutting groove grinding and to increase the precision of the cutting groove grinding.

(Embodiment 2)
The positions of the upper base 111, the lower base 112, and the oblique sides 113, 114 forming the trapezoidal shape as described above, that is, the distance from the center O, may be set in various ways, but may be set to be equidistant (so that each side is tangent to the inscribed circle 102) as shown in FIG. 6. In this case, the amount of cutting groove penetration during grinding is equal for all sides, so that, for example, in a program for operating a grinding machine, grinding can be easily performed using a common routine for a predetermined amount of cutting. In addition, by simplifying the processing, it becomes easier to perform cutting groove grinding and to increase the accuracy of cutting groove grinding. It is not limited to setting the distance from the center O to be equal for all four sides, and two or more sides may be set to be equidistant from the center.

(Embodiment 3)
The trapezoidal shape as described above does not necessarily have to be formed in the same manner over the entire length of the working part 100a, but may be formed in a cross-sectional shape in which the vertices of both ends of the lower base 112 remain along the arc of the virtual circle 101, as shown in Fig. 7, in a predetermined range of the tip of the working part 100a. By forming the cross-sectional shape in this manner, it is possible to easily reduce the feeling of being pulled in and improve the root canal tracking, for example, especially in the case of a rotary file.

(Embodiment 4)
The dimensions and angles of each side of the trapezoid may be different between the base end side and the tip end side of the working part 100a. Specifically, for example, the working part 100a may be formed in a shape as shown in FIG. 5 near the tip end, while the working part 100a may be formed in a shape as shown in FIG. 8 near the base end. That is, in the case of FIG. 5 and FIG. 8, the angle between the diameter of the virtual circle 101 passing through the apex 123 and the base 112, and the angle between the diameter of the virtual circle 101 passing through the apex 124 and the oblique side 114 are set so that the angle at the tip (FIG. 5) is larger than the angle at the base end (FIG. 8). As a result, when the rotation direction is mainly counterclockwise in FIG. 8, the dental file 100 near the tip maintains a moderate cutting ability, has high torsional rigidity, and has a so-called stiffness, making it easy to transmit the rotational force to the tip. In addition, it is easy to form a dental file 100 with high cutting ability, flexibility, and dischargeability toward the base end.

Here, if the main rotation direction during normal use of the dental file 100 is the direction in which cutting waste from the working part 100a is carried towards the base, that is, specifically, for example, if the helix of the dental file 100 is a right-handed thread, the main rotation direction is counterclockwise as viewed from the tip side, then when rotating in such a direction, the base 112 at the apex 123 and the oblique side 114 at the apex 124 will produce a cutting action as the dental file 100 rotates. Note that the rotation direction of the dental file 100 is not limited to the above-mentioned direction, and it may be used in a mode that includes reverse rotation or in a mode in which the rotation direction alternates.

When the main rotation direction in FIG. 8 is clockwise, the angle between the diameter of the imaginary circle 101 passing through vertex 123 and the oblique side 113, and the angle between the diameter of the imaginary circle 101 passing through vertex 124 and the base side 112 are set so that the angle at the tip end (FIG. 5) is larger than the angle at the base end (FIG. 8), thereby obtaining the same effect as described above for the main rotation direction being counterclockwise. Also, the above angle setting may be performed for only one of the vertices 123 or 124.

100 Dental file 100a Working part 100b Shaft 101 Virtual circle 102 Inscribed circle 111 Upper base 112 Lower base 113 Hypotenuse 114 Hypotenuse 121 Vertex 122 Vertex 123 Vertex 124 Vertex 131 Land portion 132 Land portion

Claims (4)

1. A dental file having a spirally shaped working portion,
A cross-sectional shape perpendicular to the longitudinal direction is a trapezoid having an upper base, a lower base, and first and second oblique sides;
With respect to an imaginary circle whose center is the longitudinal axis and whose diameter decreases from the base end to the tip end,
The vertices of both ends of the lower base are located on the virtual circle,
A dental file characterized in that the vertices of both ends of the upper base are set to be located inside the imaginary circle. 2. The dental file of claim 1,
A dental file characterized in that, in at least a portion of the cross-sectional shape in the longitudinal direction, the distances from the center of the imaginary circle to the upper base, the lower base, and the first and second hypotenuses are set equal to each other. A dental file according to any one of claims 1 to 2,
A dental file characterized in that the cross-sectional shape of the tip portion has land portions near the vertices of both ends of the lower base of a trapezoid that follow the arc of the imaginary circle. A dental file according to any one of claims 1 to 3,
A dental file characterized in that an angle formed by a diameter of the imaginary circle passing through a vertex of at least one end of the lower base and at least one of the hypotenuses having the lower base and the vertex as endpoints is set to increase from the base end to the tip end.

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